1. Field of the Invention
This invention relates generally to an optical proximity switch, particularly to adjusting the setting of a potentiometer.
2. Description of the Prior Art
Optical proximity switches are used as contactless electronic switches for monitoring purposes. They are used also in the automation industry.
Optical proximity switches include an optical transmitter; usually an LED or laser diode, for transmitting a light signal to a monitoring area; and at least one photodetector for receiving the light signal transmitted. If an object is located in the monitoring area, the light signal is interrupted or reflected, at least it is attenuated or its polarization direction changes. If the influence of the object on the light signal reaches a degree determined by a switching threshold, then a switching signal is tripped.
Switchgear of this kind is produced and sold in various embodiments and is commercially available from ifm electronic gmbh of Essen, Germany.
In an early stage of development the switching threshold was set with potentiometers, often multispeed spindle potentiometers because of their higher resolution. Later, especially with the arrival of microcontrollers, devices with automatic switching point setting by so-called teach-in methods came onto the market.
For displaying the set switching point, either self-illuminating LEDs and/or passive LCD displays are used. Self-illuminating LEDs and/or passive LCD displays increases not only the production costs but also the operating costs and put a thermal burden on the devices as well. Moreover, customers want the device setting to be recognizable in the currentless state even without aids, and want to set the device in the currentless state before installing it.
German Patent Disclosure DE 10 2009 048 389 A1 shows an arrangement for detecting more than one revolution. Especially the gear construction in FIG. 6 discloses a set of solutions that is suitable for attaining the object of the present invention. The magnetic coupling can be dispensed with. Its lack of a display unit is a disadvantage.